Learn English – “At the drop of a hat”

Strictly speaking "souls on board" has a different meaning from all of your other constructions.

"There are 150 on board" can't be turned into a question. The official phraseology is "say souls on board [and fuel remaining]" -- there are no questions in ATC official phraseology. "Say number onboard" really is ambiguous and could be understood to mean only passengers.

Strictly speaking, "people" or "humans" is ambiguous too. For example is a dead person still a person? This is a rational concern with "say passengers onboard" (which might not include crew) and "say number onboard" (which is ambiguous).

But nobody with any functioning brain cells could possibly misunderstand "say persons onboard". This is an officially-acceptable civil aviation alternative to "souls onboard", as are the written abbreviations SOB and POB.

There is actually a dispute over whether "souls on board" should count entire human remains. The civil aviation standard is that a dead body is cargo and not counted. The RAF standard, and that of many other military organizations, is that dead bodies are "souls" being returned and they count them. Whether that makes sense depends on exactly what the figure is for. Is it to know how many bodies to look for? Is it to know how many people perished? (Perhaps it does not matter so long as both sides know what they're doing, and they make this a point of respect.)

In any event, no more detailed origin is known, as far as I've been able to tell. There's just lots of speculation. It was definitely originally a nautical term.

You catch more flies with honey than vinegar or, sometimes you catch more flies with honey is an English proverb. It doesn't have a counter-intuitive meaning--if you are trying to catch flies, you are literally going to attract more with honey. That is, you're going to get what you want (in the proverb flies, but in life any goal) with sweetness rather than acidity.

This answer explains it similarly:

Flies represents anything you want to achieve. Honey (sweet) represents anything pleasant that you do to get what you want. Vinegar (sour) represents anything unpleasant that you do to get what you want. It tells you to use nice methods rather than unkind methods in dealing with other people.

This is a saying that means: you will be more successful in life being sweeter, or nice rather than being, mean to people, not nice and doing hurtful, dishonest things in life.

This forum makes some guesses at its origins, noting:

The proverb has been traced back to G. Torriano's 'Common Place of Italian Proverbs' . It first appeared in the United States in Benjamin Franklin's 'Poor Richard's Almanac' in 1744, and is found in varying forms..." From "Random House Dictionary of Popular Proverbs and Sayings" by Gregory Y. Titelman (Random House, New York, 1996).